Shell Programming and Scripting

Hi all,

I am tring to write a script which should read the first line of the file and perform some task. Once the task is completed the next line of the file should be read the task should be performed.
So is it possible to have a counter sort of thing, in sed or awk, which would increment and hence cause the next line to be read?
Following is how I thought of doing it, but it does not work as I can't assign value to $C to get to read a line:

Code:

C=1 #counter
while true
do
 LOG=`sed '$C!d' /var/log/somelog.log`
 #
 perform the task on $LOG
 #
 C=`expr $C + 1`
done

Thanks

Basic scripting concept:

Code:

while read line
do
  #perform the task on "$line"
done < /var/log/somelog.log

Thanks for the reply danmero.

I had tried that earlier. When the script reads thru somelog.log and reaches EOF it exits. But I don't want it to exit. If the EOF is reached the script should wait till new line is added to somelog.log and then perform the task. Also the new to somelog.log would be added at random intervals.

Any suggestions on how to have the script wait where it stopped rather than exiting and continue when the new line is added?

Thanks.

you could tail -f the log and parse that through the script.

Should work....alternative method is to remeber where you got to in the file (line count) and then run your script at intervals starting where you left off - just be careful handling logrotates

If I tail -f the log and parse it through the script when a new line is added to the log the script exits.
I haven't tried the alternative step yet as I am not familiar with logrotates.
Would there be any other way to do this?

Thanks.

hmm - try something like:

Code:

#  tail -f infile | while read line; do echo $line | tr "[a-z]" "[A-Z]"; done
HELLO
WORLD

where infile was an empty file, and I simply did:

Code:

#  echo hello >> infile
#  echo world >> infile

Thanks for the reply tytalus.

I guess this would not work for me as my script contains 10 logics in it. So I took another route and using cron and ls and moving the files around once the job is over I got it to do the job. But it would have been nice and easier if I could just figure out a way to do this as I wanted. Still I will continue to read thru and see if I can do it the way I wanted to do it.

Thanks again.